/*
 Copyright  2002-2004 MySQL AB, 2008 Sun Microsystems
 All rights reserved. Use is subject to license terms.

  The MySQL Connector/J is licensed under the terms of the GPL,
  like most MySQL Connectors. There are special exceptions to the
  terms and conditions of the GPL as it is applied to this software,
  see the FLOSS License Exception available on mysql.com.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; version 2 of the
  License.

  This program is distributed in the hope that it will be useful,  
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  02110-1301 USA



 */
package testsuite.perf;

import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;

import testsuite.BaseTestCase;

/**
 * Base class for performance test cases. Handles statistics.
 * 
 * @author Mark Matthews
 */
public abstract class BasePerfTest extends BaseTestCase {
	// ~ Static fields/initializers
	// ---------------------------------------------

	/**
	 * Confidence interval lookup table, indexed by degrees of freedom at 95%.
	 */
	private static final double[] T95 = { 12.706, 4.303, 3.182, 2.776, 2.571,
			2.447, 2.365, 2.306, 2.262, 2.228, 2.201, 2.179, 2.160, 2.145,
			2.131, 2.120, 2.110, 2.101, 2.093, 2.086, 2.080, 2.074, 2.069,
			2.064, 2.060, 2.056, 2.052, 2.048, 2.045, 2.042 };

	/**
	 * Confidence interval lookup table, indexed by degrees of freedom at 99%.
	 */
	private static final double[] T99 = { 63.657, 9.925, 5.841, 4.604, 4.032,
			3.707, 3.499, 3.355, 3.250, 3.169, 3.106, 3.055, 3.012, 2.977,
			2.947, 2.921, 2.898, 2.878, 2.861, 2.845, 2.831, 2.819, 2.807,
			2.797, 2.787, 2.779, 2.771, 2.763, 2.756, 2.750 };

	static NumberFormat numberFormatter = NumberFormat.getInstance();

	static {
		numberFormatter.setMaximumFractionDigits(4);
		numberFormatter.setMinimumFractionDigits(4);
	}

	// ~ Instance fields
	// --------------------------------------------------------

	/**
	 * List of values for each iteration
	 */
	private List testValuesList = new ArrayList();

	private double confidenceLevel = 95; // 95% by default

	private double confidenceValue = 0;

	private double intervalWidth = 0.1;

	private double meanValue = 0;

	private double squareSumValue = 0;

	private double sumValue = 0;

	private double variationValue = 0;

	/**
	 * The number of iterations that we have performed
	 */
	private int numIterations = 0;

	// ~ Constructors
	// -----------------------------------------------------------

	/**
	 * Creates a new BasePerfTest object.
	 * 
	 * @param name
	 *            the testcase name to perform.
	 */
	public BasePerfTest(String name) {
		super(name);
	}

	// ~ Methods
	// ----------------------------------------------------------------

	/**
	 * Returns the meanValue.
	 * 
	 * @return double
	 */
	public double getMeanValue() {
		return this.meanValue;
	}

	/**
	 * Sub-classes should override this to perform the operation to be measured.
	 * 
	 * @throws Exception
	 *             if an error occurs.
	 */
	protected abstract void doOneIteration() throws Exception;

	/**
	 * Returns the current confidence level.
	 * 
	 * @return the current confindence level.
	 */
	protected double getCurrentConfidence() {
		return (this.intervalWidth - this.confidenceValue) * 100;
	}

	/**
	 * Returns the current margin of error.
	 * 
	 * @return the current margin of error.
	 */
	protected double getMarginOfError() {
		return getConfidenceLookup()
				* (getStandardDeviationP() / Math.sqrt(this.numIterations));
	}

	/**
	 * Returns the current STDDEV.
	 * 
	 * @return the current STDDEV
	 */
	protected double getStandardDeviationP() {
		if (this.numIterations < 1) {
			return 0;
		}

		return Math
				.sqrt(((this.numIterations * this.squareSumValue) - (this.sumValue * this.sumValue))
						/ (this.numIterations * this.numIterations));
	}

	/**
	 * Adds one test result to the statistics.
	 * 
	 * @param value
	 *            a single result representing the value being measured in the
	 *            test.
	 */
	protected void addResult(double value) {
		this.numIterations++;
		this.testValuesList.add(new Double(value));

		this.sumValue += value;
		this.squareSumValue += (value * value);
		this.meanValue = this.sumValue / this.numIterations;
		this.variationValue = (this.squareSumValue / this.numIterations)
				- (this.meanValue * this.meanValue);

		// Can only have confidence when more than one test
		// has been completed
		if (this.numIterations > 1) {
			this.confidenceValue = this.intervalWidth
					- ((2.0 * getConfidenceLookup() * Math
							.sqrt(this.variationValue
									/ (this.numIterations - 1.0))) / this.meanValue);
		}
	}

	/**
	 * Calls doIteration() the <code>numIterations</code> times, displaying
	 * the mean, std, margin of error and confidence level.
	 * 
	 * @param numIterations
	 *            the number of iterations to perform ( < 30)
	 * @throws Exception
	 *             if an error occurs.
	 */
	protected void doIterations(int numIterations) throws Exception {
		for (int i = 0; i < numIterations; i++) {
			doOneIteration();
		}
	}

	/**
	 * Reports the current results to STDOUT, preceeded by
	 * <code>additionalMessage</code> if not null.
	 * 
	 * @param additionalMessage
	 *            the additional message to print, or null if no message.
	 */
	protected synchronized void reportResults(String additionalMessage) {
		StringBuffer messageBuf = new StringBuffer();

		if (additionalMessage != null) {
			messageBuf.append(additionalMessage);
			messageBuf.append(": ");
		}

		messageBuf.append(" mean: ");
		messageBuf.append(numberFormatter.format(this.meanValue));
		messageBuf.append(" stdevp: ");
		messageBuf.append(numberFormatter.format(getStandardDeviationP()));
		messageBuf.append(" m-o-e: ");
		messageBuf.append(numberFormatter.format(getMarginOfError()));

		System.out.println(messageBuf.toString());
	}

	private double getConfidenceLookup() {
		if (this.confidenceLevel == 95) {
			return T95[this.numIterations - 1];
		} else if (this.confidenceLevel == 99) {
			return T99[this.numIterations - 1];
		} else {
			throw new IllegalArgumentException(
					"Confidence level must be 95 or 99");
		}
	}
}
